Various embodiments are based on a circuit arrangement as is described in the document EP 0 748 146 A1. In the circuit arrangement disclosed therein, an inverter provides an AC supply voltage for a low-pressure gas discharge lamp (fluorescent lamp). A resonant inductor is coupled to the inverter. A resonant capacitor is coupled in parallel with the low-pressure gas discharge lamp. All of the operational functions of the gas discharge lamp are controlled via the inverter. Once the circuit arrangement has been brought into operation (this takes place by applying an AC system voltage to a switched mode power supply coupled to the inverter), the inverter is operated at a frequency which is not only above the open-circuit resonant frequency of the resonant circuit (resonant inductor and resonant capacitor), but also above a starting frequency, during a preheating phase for gentle starting of the gas discharge lamp. During this preheating phase, a preheating current flows via the electrodes of the gas discharge lamp. This current is intended to heat the electrodes to emission temperature. Since the frequency of the AC supply voltage during the preheating phase is greater than the starting frequency of the gas discharge lamp, premature starting of the gas discharge lamp is prevented. That is to say that, above the resonant frequency of the resonant circuit, the amplitude of the voltage across the resonant capacitor is indirectly proportional to the frequency.
The document US 2006/0267519 A1 likewise describes a circuit arrangement for operating a low-pressure gas discharge lamp. Said document deals with the problem of protecting a person who is at the ground reference potential and who is touching the gas discharge lamp from an electric shock. This document takes the approach of connecting the reference potential of the gas discharge lamp to the reference potential of the inverter via a parallel circuit comprising a switch and a capacitor. The switch is only closed when the gas discharge lamp has started correctly. Otherwise, the switch remains open, with the result that the connection of the gas discharge lamp is largely decoupled at a low frequency from the reference potential of the inverter. The capacitor which is coupled in parallel with the switch is necessary for ensuring this decoupling between the connection of the gas discharge lamp and the reference potential of the inverter.